1. Field of the Invention
The present invention relates to an apparatus for treating the surfaces of wafers of semiconductor or glass with a vaporous agent so as to improve their surface properties. For example, the surface of a wafer is treated to enhance its ability to a adhere to photoresist.
2. Description of the Prior Art
In order to treat the surfaces of a wafer with a vaporous agent, hereinafter referred to merely as "vapor", the important thing is to cover the entire surface with the vapor evenly. The applicant has devised an apparatus for evenly spreading a vapor over the surface of a wafer, which is disclosed in Japanese Utility Model Application Kokai No. 61-119341 (U.S. Pat. No. 4,693,211).
To explain the background of the present invention this previous apparatus will be described with reference to FIG. 3.
The apparatus includes a heating plate 2 on which a wafer 1 is placed. A cover 10 covers the wafer 1 on the heating plate 2 to form a treating chamber 11 therebetween. A tube 14 is provided for introducing a vapor into the treating chamber 11. A discharge chamber 8 is provided around the heating plate 2. The discharge chamber includes slits 8a. Excess vapor is led into the discharge chamber 8 throught the slits 8a. The cover 10 is moved up and down by a power driving unit(not shown). When the cover 10 is placed over the heating plate 2, a gap 9 is formed therebetween and the excess vapor is allowed to pass therethrough.
The wafer 1 is conveyed to and from the heating plate 2 by means of a conveyor belt 16. When the wafer 1 is to be placed on the heating plate 2, the conveyor belt sinks into a recess 17, leaving the wafer 1 on the heating plate 2. The heating plate 2 is provided with bores 3 through which the wafer 1 on the plate 2 is sucked by a vacuum member (not shown). The treating chamber 11 is divided into an upper section 11a and a lower section by a partition 12, the partition is provided with pores 13 adapted to evenly distribute the vapor in the chamber 11. The reference numeral 15 denotes a heat shield.
The vapor is introduced into the treating chamber 11 through the tube 14. Within the treating chamber 11, the vapor contacts the surface of the wafer 1. Excess vapor escapes from the treating chamber 11 through the gap 9 and is directed into the discharge chamber 8. If the vapor flow within the treating chamber 11 is disturbed, the vapor will not evenly contact the surface of the wafer. The apparatus of FIG. 3 is devised so that the slits 8a are located at a distance from the wafer 1 so as to avoid the influence of suction acting in the slits, and to minimize turbulence of the treating vapor.
However, under within the apparatus of FIG. 3, disturbance of excess vapor is likely to occur at the gap 9 in response to any change occurring in the flow and the pressure of the discharging excess vapor when the excess vapor passes through the slits 8a. This disturbance is unavoidable because of the small cross-section of the gap 9. The disturbance outside the treating chamber 11 prevents the vapor therein from contacting the surface of the wafer evenly. To make up for the uneven contact of vapor it becomes necessary to prolong the treating period, or to increase the amount of the treating vapor.